Cure of rubber with trihaloisocyanuric acid

ABSTRACT

1. A METHOD OF ADHERING TWO BODIES TOGETHER COMPRISING APPLYING TO A SURFACE OF AT LEAST ONE OF SAID BODIES AN ADHESIVE CEMENT COMPRISING AN OLEFINICALLY UNSATURATED VULCANIZABLE ELASTOMER WHICH IS A COPOLYMER OF AT LEAST TWO DIFFERENT ALPHA-MONOLEFINS WITH AT LEAST ONE COPOLYMERIZABLE POLYENE IN ADMIXTURE WITH A TRIHALOISOCYANURIC ACID IN AMOUNT EFFECTIVE TO CURE THE SAID ELASTOMER DISSOLVED IN AN INERT VOLATILE ORGANIC SOLVENT, BRINGING SAID BODIES TOGETHER WITH SAID ADHESIVE THEREINBETWEEN, AND SUBJECTING THE ASSEMBLY TO CURING TEMPERATURE TO CURE THE ADHESIVE AND THEREBY ADHESIVELY SECURE THE BODIES TOGETHER.

United States Patent 3,843,487 CURE 0F RUBBER WITIIRIHALOIS0CYANURIC ADon V. Perkins, South Bend, Ind., assignor to Uniroyal, Inc., New York,N.Y. N0 Drawing. Filed Jan. 22, 1973, Ser. No. 325,907

Int. Cl. C08c 17/20, 17/28; C08d 13/20, 13/28 U.S. Cl. 156334 6 ClaimsABSTRACT OF THE DISCLOSURE Rubber, such as EPDM, NR, SBR, can be curedby the action of a trihaloisocyanuric acid (e.g., trichloro isocyanuricacid). Elevated temperature is not necessary. EPDM compositionscontaining this curative are useful as adhesives, sealants or caulkswhich cure at ambient temperature. Cured sheets of EPDM can be cementedtogether with the adhesive. A solution of trihaloisocyanuric acidapplied to an EPDM sheet causes the sheet to cure. Translucent films orfilms with high light transmission qualities are obtainable.

This invention relates to the cure of rubber, using a trihaloisocyanuricacid as the curing agent.

W. Hoffmann, Vulcanization and Vulcanizing Agents" (Palmerton PublishingCo., New York, N.Y., 1967), page 309, refers to vulcanization withchlorine-containing compounds, but not with trihaloisocyanuric acids.

In accordance with the invention, it has now been found that rubber canbe cured with a trihaloisocyanuric acid. The cure can be effected underambient conditions. The rubber compositions of the invention containinga trihaloisocyanuric acid are particularly useful in the form of cementsor adhesives, or high-solids sealants or caulking compositions, whichare self-curing at ordinary ambient temperatures. The adhesivecomposition of the invention can be used to adhere two elastomericbodies together. One advantageous feature of the invention is thattranslucent vulcanizates, or vulcanizates having high light transmissionqualities, are obtainable.

The rubber employed in the invention may be an olefinically unsaturatedelastomer, whether highly unsaturated as in such typical conjugateddienehomopolymers or copolymers as natural rubber (basically polyisoprene) ora rubber of low unsaturation, particularlyethylenepropylene-non-conjugated diene elastomer, hereinafter referredto as EPDM. These unsaturated elastomers are commonly termedvulcanizable rubbers, in recognition of the fact that they can bevulcanized with sulfur and other vulcanizing agents. EPDM, which is thepreferred elastomer in this invention, may be described more generallyas a copolymer of at least two different alpha-monoolefins with at leastone copolymerizable polyene which serves to confer unsaturation on thecopolymer. Ordinarily one of the alpha-monoolefins is ethylene, whilethe other is ordinarily propylene, although other pairs ofalphamonoolefins may be used. The polyene employed is frequently adiene, and although conjugated dienes can be used, best results areordinarily obtained with non-conjugated dienes, whether an open-chaindiolefin as in 1,4- hexadiene or a cyclic diene as in such bridged ringdienes as dicyclopentadiene and the alkylene or alkylidene norbornenes(e.g., methylene norbornene, ethylidene norbornene, etc.), as describedfor example in U.S. Pat. 3,562,228, Matthews et al., Feb. 9, 1971. Morethan one diene (e.g., dicyclopentadiene plus -ethylidene-2-norbornene)can be used. More than one EPDM may be used in the composition of theinvention, if desired.

3,843,487 Patented Oct. 22, 1974 In practicing the invention, the rubberis compounded with a trihaloisocyanuric acid, which has the formulawherein X X and X are the same or different halogen, usually chlorine orbromine, preferably chlorine, such as tribromoisocyanuric acid,trichloroisocyanuric acid, and the like.

The trihaloisocyanuric acid is employed in amount effective to cure orcross-link the elastomer in accordance with the invention. For thispurpose the trihaloisocyanuric acid is frequently employed in amount ofat least about 2 parts per parts by weight of the rubber, particularlywhen the trihaloisocyanuric acid is mixed into the rubber composition,but smaller concentrations may also be effective, for example when thetrihaloisocyanuric acid is introduced by diffusion (e.g., by applicationof a solution of the trihaloisocyanuric acid to the surface of a solidrubber body), as will be explained in more detail below. Larger amountsof trihaloisocyanuric acid (e.g., 10 parts or more per 100 of rubber)may be used, a preferred amount usually being about 4 to 8 parts.

The curable rubber composition of the invention may if desired be purelya gum stock, containing only the trihaloisocyanuric acid curative.Alternatively, the rubber composition of the invention may contain othercompounding ingredients such as one or more fillers (e.g., carbon black,silica, zinc oxide, etc.). The amount of filler may vary widely, forexample, from 0.5 to parts per 100 parts by weight of the elastomer.

In one preferred practice of this invention the composition takes theform of a cement or adhesive comprising the described ingredientsdissolved and/or dispersed in any suitable conventional inert volatileorganic solvent or mixture of solvents. Extender oils or otherplasticizing or softening substances may also be present. The proportionof solids in the cement is not critical and frequently ranges from 20 to40%, by weight. The cement may be applied to bodies (e.g., elastomers,wood, textiles, etc.) to be adhered together by any suitableconventional method, such as brushing, spraying, roller coating, knifespreading, etc. In practice the trihaloisocyanuric acid is preferablywithheld from the cement until just prior to use, and then added as asolution in a small amount of the solvent, usually cyclohexanone, toobtain better dispersion of the acid in the mixture. The cement may bepainted, spread, or otherwise applied onto elastomeric bodies, such assheets, molded objects, etc., prior to lamination. Upon curing of thecement the elastomeric bodies are found to be firmly adhered together.The elastomeric objects which are adhered with the aid of the cement ofthe invention may be either uncured or previously cured elastomer. Theelastomer to be adhered by the cement may be EPDM as previously defined(an example of a suitable EPDM vulcanizate is disclosed in U.S. Pat.3,330,790, Chambers, July 11, 1967, Example 1, Stock B cured 15 minutesat 320 F.), or other conventional rubber or elastomeric material,including the rubbery polymers of conjugated dienes, such as butadiene,isoprene, chlorobutadiene, etc., whether homopolymers as in polyisoprene(natural or synthetic), polybutadiene, polychloroprene and the like, orcopolymers as in copolymers of such dienes with one or morecopolymerizable monoethylenically unsaturated monomers (e.g., styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, acrylic ormethacrylic acids or esters thereof, isobutylene, vinylpyridine, etc.)as in butadiene-styrene copolymer, butadiene-acrylonitrile copolymer,isoprene-isobutylene copolymer, whether emulsion-prepared orsolution-prepared, stereospecific or otherwise. As indicated, theseelastomers may be adhered either in the cured (e.g., sulfur-cured,peroxide-cured, or otherwise cured) or uncured state, using the cementof the invention. Best results are usually obtained if the elastomericsurfaces to be adhered are first buffed or otherwise roughened, prior toapplication of the cement, particularly if the elastomer has previouslybeen cured. Sheets of cured EPDM coated with the cement and lapped toform a seam become strongly adhered together upon cure of the cement,especially cement based on EPDM. In this manner weather-resistant,waterproof covering may be produced on roofs and the like.

The cements or solutions may also be used as coatings or for makingdipped goods or cast films, sheets, or the like. Films cast from suchcements onto a suitable release surface form cured vulcanizates in 1 to6 hours at ambient temperatures (e.g., 72 F.). In general, this form ofthe invention usually involves applying the cement to a suitable formingsurface, evaporating the solvent, subjectmg to ambient temperature tocure the elastomer and removing the formed body from the formingsurface.

In another preferred embodiment of the invention the composition maytake the form of a sealant or caulking composition, usually having aplastic or pasty consistency at room temperature. For this purposevarious conventional softening and/or plasticizing substances may beincorporated in the composition. Thus, caulks, sealants and sealers maybe prepared by kneading an elastomer with filler, oils, solvents until aknife-spreadable gum is produced, after which the trihaloisocyanuricacid curative is introduced and the caulk is ready for immediate use.The caulk or sealant is introduced into a space or cavity to be caulkedor sealed, whereupon curing for 2 to 4 days at ambient conditionsproduces tough vulcanizates. This form of the invention is particularlyuseful for such sealant or caulking applications as weatherproofing ofbuildings, windows, etc., expansion joints for pavements, filling seamsof boats, etc.

An advantageous way of practicing the invention involves introducing thetrihaloisocyanuric acid curative to the elastomer by diffusion.According to this method of making a cured body, the elastomer is shapedin a desired shape, and the trihaloisocyanuric acid, suitably in theform of a solution in cyclohexanone, is applied to the surface of theelastomer. The curative diffuses into the elastomer and cure takesplace.

The curing method of the invention operates, as indicated, at ordinaryambient or room temperature. Outdoors in cold weather (e.g., F.) thesystem is operative although a longer period of time will of course berequired to reach the same level of cure as is obtained indoors or inwarm weather. Ambient temperature as used herein includes suchmoderately elevated surface temperatures as may sometimes be encounteredin working in sunlight for example (e.g., 110 F. or more). In general,the lower the concentration of curatives in the composition the longerthe cure cycle required to achieve a given level of cure at a particularambient temperature. At lower ambient temperatures higher levels ofcuratives may be desirable whereas at more elevated ambient temperatureslower concentrations of curatives may be used to achieve a satisfactorystate of cure within a desired time. Although ordinarily not necessary,conventional elevated curing temperatures may also be applied, forexample when a very low concentration of curative is employed or whenthe rubber employed is one which reacts only slowly (e.g., butyl rubber,NBR).

The reaction between natural rubber and trichloroisocyanuric acid as thesole curing agent at room temperature may be demonstrated by adding 5pphr, (parts per hundred parts by weight of rubber) oftrichloroisocyanuric acid (dissolved in a small amount of cyclohexanone)to a stirred 5% solution of Washed smoked sheet in hexane. A stringymass of crosslinked rubber wraps itself immediately around the mixerblade. There is no measurable increase in viscosity of the remainingsolution after 24 hours. Repetition of the procedure with a 5% solutionof SBR 1500 gives a similar result. Such reactions are useful in theformation of rubber fibers (see US. Pat. 2,953,839, Kohrn et al., Sept.27, 1960).

Using a 5% solution of nitrile rubber (Paracril C, trademark) in methylethyl ketone, addition of 2 pphr. of trichloroisocyanuric acid producessmall soft lumps of crosslinked rubber immediately. The body of thesolution remains clear with no detectable change in viscosity after 24hours. 5% of butyl rubber 268 dissolved in hexane gives a similar resultupon addition of 2 pphr. of trichloroisocyanuric acid.

Similarly, trichloroisocyanuric acid is capable of crosslinking withEPDM polymers containing any of the three main types of pendant dienegroups, namely, 1,4-hexa diene, dicyclopentadiene and norbornenes, butthe preferred dienes are the 1,4-hexadiene and dicyclopentadiene types.

The following examples, in which all quantities are expressed by weightunless otherwise indicated, will serve to illustrate the practice of theinvention in more detail.

EXAMPLE 1 A 5% solution of EPDM is prepared. The EPDM contains 65%ethylene, 30% propylene, and 5% dicyclopentadiene, and has a Mooneyviscosity of 60 ML-4-2l2" F. Six pphr. of trichlorisocyanuric acid(dissolved in a small amount of cyclohexanone) is stirred into thesolution. Within about 2 minutes the viscosity of the solution hasincreased, from an initial value of about 97.5- cps. (centipoises,measured by a Brookfield viscometer, No. 1 spindle at 20 r.p.m.) toabout cps. After about 10 minutes the viscosity is about 248 cps; at 30minutes the viscosity has increased to about 475 cps.

A film is cast from the solution and allowed to age 14 days at roomtemperature, after which the tensile strength, elongation at break andhardness are measured, with the results noted in Table I, under EPDM-1.Table I also shows, for comparison, the result obtained on a 14 day oldfilm cast from the same EPDM solution containing no trichloroisocyanuricacid curative; this control film is too soft to test. Table I furthershows the results obtained by substituting two other EPDMs for EPDM-1,as follows: EPDM-2 which contains 53% ethylene, 42% propylene, and 5%5-ethylidene-2-norbornene, and has a Mooney viscosity of 55 ML-4-212 F.;EPDM-3 which contains 48% ethylene, 47% propylene, and 5%S-ethylidene-Z-norbornene, and has a Mooney viscosity of 45 ML-4212 F.

TABLE 1 Physical properties on 5% solutions of EPDM polymers (noloading) containing triehloroisocyanuric acid as the sole vulcanizationagent cast into films and allowed to age 14 days at room temperatureEPDM-1 EPDM-2 EPDM-3 6 pphr. 6 pphr. 5 pphr. Property No acid acid Noacid acid No acid acid Tensile, p.s.i 'Ioo soft to test-. 1, 300 Toosoft to test.-. 1, 126 Too soft to test..-" 747 Elongation, percentdo620 ..--.do 940 d 880 Hardness, Shore A do 40 ..---do 43 -do 38 The castfilms of the invention cured with trichlorocyanuric acid have aremarkable characteristic which is not attainable by any roomtemperature cure system to date, as far as the inventor is aware,namely, translucency or light transmitting qualities (as defined forexample in US. Pat. 3,408,320, Brucksch, Oct. 29, 1968, whereintransparent EPDM composition cured at elevated temperature aredisclosed). The curative imparts no color to the compound, in contrastto the discoloration experienced with other room temperature curingsystems utilizing GMF to effect a cure. Thus, cured articles having alight color can be made, filled for example with such mineral fillers assilica (e.g., Hi Sil 215 [trademark]), hydrated calcium silicate (e.g.,Silene D [trademark]), Zinc oxide, or the like, if desired.

EXAMPLE 2 Three masterbatches are prepared according to the followingrecipes:

The EPDM-1 and EPDM-2 are as previously identified. EPDM-4 contains 51%ethylene, 39% propylene, and 5-ethylidene-2-norbornene and has a Mooneyviscosity of 60 ML4-212 F. The oil is a petroleum hydrocarbon extenderor processing oil of mixed aromatic (10%) naphthenic (42%) andparafiinic (48%) type, API (American Petroleum Institute) gravity, 21.5.The masterbatches shown are mill mixed, then cut into cement form attotal solids in xylene. Six pphr. of trichloroisocyanuric acid dissolvedin cyclohexanone is added to each cement, films are cast, and propertiesdetermined after days aging at room temperature, and again after heataging an additional 72 hours at 212 F., with the results shown in TableII.

TABLE II Physical property checks on 30 day 6 EXAMPLE 4 A sample ofMasterbatch A described in Example 2 is cast into a film containing notrichlorisocyanuric acid. After solvent evaporation, one-half of thesurface of the film is painted with an 8'% solution oftrichlorisocyanuric acid in cyclohcxanone. Thirty days after paintingthe surface, the Shore A hardness of the top surface of the film is 67in the treated area and in the non-treated area, indicating that asurface cure is obtained in the treated area, by ditfusion of thetrichloroisocyanuric acid curative into the stock.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A method of adhering two bodies together comprising applying to asurface of at least one of said bodies an adhesive cement comprising anolefinically unsaturated vulcanizable elastomer which is a copolymer ofat least two ditferent alpha-monoolefins with at least onecopolymerizable polyene in admixture with a trihaloisocyanuric acid inamount effective to cure the said elastomer dissolved in an inertvolatile organic solvent, bringing said bodies together with saidadhesive thereinbetween, and subjecting the assembly to curingtemperature to cure the adhesive and thereby adhesively secure thebodies together.

2. A method of adhering two cured ethylene-propylenenon-conjugated dieneterpolymer rubber bodies together comprising applying to a surface of atleast one of said bodies an adhesive cement comprising an olefinicallyunsaturated vulcanizable elastomer which is anethylenepropylene-non-conjugated diene terpolymer in admixture with atrihaloisocyanuric acid in amount effective to cure said elastomerdissolved in an inert volatile organic solvent, bringing said bodiestogether with said adhesive thereinbetween, and subjecting the assemblyto ambient temperature to cure the adhesive and thereby adhesivelysecure the bodies together.

3. A method as in claim 2 in which the trihaloisocyanuric acid istrichloroisocyanuric acid.

4. A method as in claim 3 in which the diene in the said elastomer isdicyclopentadiene.

room temperature aged films cast from 20% Q 0f aS e batches A. B and 0plus physical properties on the aged films after 72 hrs. at 21Masterbatch A (EPDM-1) 20% solution in xylene Masterbatch B (EPDM-4) 20%solution in xylene Masterbatch C (EPDM-2) 20% solution in xylene plus 6pphr. plus 2 pphr. plus 4 pphr. trichloroisocyanurlctrichlorolsocyanurlc trrchloroisoeyanurlc acid acid acid 30 days at 30days at 30 days at RT plus 72 RT plus 72 RT plus 72 30 days hrs. at 30days hrs. at 30 days hrs. at Property at RT 212 F. at RT 212 F. at RT212 F. Tensile, p.s.i 1, 512 1, 249 55 700 75 2, 333 Elongation, percent180 105 300 180 420 310 Shore A hardness 67 71 55 67 58 68 5. A methodas in claim 3 in which the diene in the EXAMPLE 3 TABLE III Shearadhesion 2/min. pounds/in. of adhesion area 3-days after 10 days afterSubstrate preparation fabrication fabrication Solvent washed. 37.1 47. 0Buffed and solvent washed 43. 4 62. 4

55 said elastomer is 1,4-hexadiene.

6. A method as in claim 3 in which the diene in the said elastomer isS-ethylidene-Z-norbornene.

References Cited UNITED STATES PATENTS 3,730,951 5/1973 Brande 26077.5 B

3,403,138 9/1968 Edwards 260-88.2

3,379,707 4/1968 Lund et al. 26094.9

OTHER REFERENCES Hoffmann, W.: vulcanization and Vulcanizing Agents(Palmerton, N.Y.) 1967, pp. 260-265.

Alliger, G. and Sjothun, I. 1.: vulcanization of Elastomers (Reinhold),1964.

JOSEPH L. SCHOFER, Primary Examiner A. L. CLINGMAN, Assistant ExaminerUS. Cl. X.R.

26080.78, 94.7 HA, 94.7 N, 94.9 GA, 94.9 GB

1. A METHOD OF ADHERING TWO BODIES TOGETHER COMPRISING APPLYING TO ASURFACE OF AT LEAST ONE OF SAID BODIES AN ADHESIVE CEMENT COMPRISING ANOLEFINICALLY UNSATURATED VULCANIZABLE ELASTOMER WHICH IS A COPOLYMER OFAT LEAST TWO DIFFERENT ALPHA-MONOLEFINS WITH AT LEAST ONECOPOLYMERIZABLE POLYENE IN ADMIXTURE WITH A TRIHALOISOCYANURIC ACID INAMOUNT EFFECTIVE TO CURE THE SAID ELASTOMER DISSOLVED IN AN INERTVOLATILE ORGANIC SOLVENT, BRINGING SAID BODIES TOGETHER WITH SAIDADHESIVE THEREINBETWEEN, AND SUBJECTING THE ASSEMBLY TO CURINGTEMPERATURE TO CURE THE ADHESIVE AND THEREBY ADHESIVELY SECURE THEBODIES TOGETHER.